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According to manual page [1], posix spec [2] and source code like arch/mips/kernel/syscall.c, for historic reasons, the sys_pipe() syscall on some architectures has an unusual calling convention. It returns results in two registers which means there is no need for it to do verify the validity of a userspace pointer argument. Historically that used to be expensive in Linux. These days the performance advantage is negligible. Nolibc doesn't support the unusual calling convention above, luckily Linux provides a generic sys_pipe2() with an additional flags argument from 2.6.27. If flags is 0, then pipe2() is the same as pipe(). So here we use sys_pipe2() to implement the pipe(). pipe2() is also provided to allow users to use flags argument on demand. [1]: https://man7.org/linux/man-pages/man2/pipe.2.html [2]: https://pubs.opengroup.org/onlinepubs/9699919799/functions/pipe.html Suggested-by: Zhangjin Wu <falcon@tinylab.org> Link: https://lore.kernel.org/all/20230729100401.GA4577@1wt.eu/ Signed-off-by: Yuan Tan <tanyuan@tinylab.org> Reviewed-by: Thomas Weißschuh <linux@weissschuh.net> Signed-off-by: Willy Tarreau <w@1wt.eu>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.